1. Field of the Invention
The present invention relates to a cylinder apparatus which can be used to open and close a key by converting fluid energy supplied from a pressure fluid supply source into mechanical energy, transmitting driving force to a key through a link section disposed at a forward end of a piston rod, and inserting the key into a key groove of a workpiece.
2. Description of the Related Art
As shown in FIG. 11, a cylinder apparatus 1 has been conventionally used which includes the following mechanism as a driving source. That is, a piston 5 accommodated in a cylinder tube 4 connected between a head cover 2 and a rod cover 3 is displaced to a displacement terminal end by compressed air supplied from a pressure fluid port 20, 21. A first spring 9 installed between a pair of holding members 8a, 8b then contracts. Thereafter, the first spring 9 expands to press and return the piston 5. The piston 5 is displaced to an arbitrary position in the direction of the initial position.
If a workpiece is formed of resin, a key cannot be inserted into a key groove of the workpiece at an originally set position of the key due to an error of dimensional accuracy.
According to the conventional cylinder apparatus 1, therefore, the key position is previously determined in consideration of the error of the dimensional accuracy of the workpiece at the displacement terminal end of the piston 5. The key fits an originally set position of the key groove of the workpiece if the piston 5 is pressed and returned from the previously determined position by the expanding force of the first spring 9.
As shown in FIG. 11, the piston 5 of the conventional cylinder apparatus 1 is displaced if the piston 5 is pressed and returned by the expanding force of the first spring 9. When a pin 16 of a piston pin mechanism 15 is inserted into a recess 7 of a piston rod 6 under the action of a second spring 18, the pin 16 contacts the recess 7 of the piston rod 6 pressed and returned by the first spring 9. Thus, the pin 16 and the recess 7 are fastened to one another to set a displacement amount of the piston 5 in the direction of the initial position.
However, it is impossible for the cylinder apparatus 1 thus constructed to unlock the pin 16 easily and conveniently due to contact resistance between the side surface of the recess 7 of the piston rod 6 and the side surface of the pin 16.
According to the conventional cylinder apparatus 1, further, a first three-port solenoid-operated valve 22a is energized at the initial position shown in FIG. 12 and a second three-port solenoid-operated valve 22b is opened to the atmospheric air. The pressure fluid is supplied from a fluid supply source 23 into the cylinder apparatus 1 to displace the piston 5 to the displacement terminal end position (see FIG. 13). Further, the piston 5 is slightly displaced in the direction of the initial position with the respective pair of three-port solenoid-operated valves 22a, 22b being switched to be opened to the atmospheric air (see FIG. 14).
In the above procedure, the pin 16 is inserted into the recess 7 (see FIG. 11) of the piston rod 6 to position the piston 5. As shown in FIG. 15, the two three-port solenoid-operated valves 22a, 22b need to be provided for simultaneously pressurizing the pressure fluid from the pressure fluid ports 20, 21 so as to release the side surface of the recess 7 of the piston rod 6 and the side surface of the pin 16 from the fastened state thereof. Therefore, the number of components and steps is increased, and the control circuit becomes complicated.
It is a general object of the present invention to provide a cylinder apparatus which can hold or unlock a piston easily and conveniently even if an error of dimensional accuracy or the like occurs.
A principal object of the present invention is to provide a cylinder apparatus which can insert a key into a key groove of a workpiece easily and conveniently and to unlock a pin from a recess of a piston rod with ease.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.